R help - Aug 2011 - Any alternatives to draw.colorkey from lattice package?

Hello!

I?d like to have a continuous color bar on my lattice xyplot with colors lets
say from topo.colors such that it has ticks & labels at few specific points
only.

Right now I use do.breaks & level.colors with somewhat large number of
steps. The problem is that color change point doesn?t necessary correspond to
the value I?d like to label. Since I have many color steps and I don?t need high
precision I generate labels like this

labels <- ifelse( sapply(at,function(x) any(abs(att-x)<.03)) ,
sprintf("depth= %s ft", at), "")

, where `att` has mine points of interest on color scale bar and `at`
corresponds to color change points used with level.colors . It is a bit
inconvenient as I have to adjust threshold `.03`, number of color steps so that
it labels only adjacent color change point with my labels.

Q: Are there any ready to use functions that would generate some kind of
GRaphical OBject with continuous color scale bar/key with custom at/labels such
that it would work with `legend` argument of xyplot from lattice?

Mikhail

On 08/13/2011 04:34 AM, Mikhail Titov wrote:
> Hello!
>
> I?d like to have a continuous color bar on my lattice xyplot with colors
lets say from topo.colors such that it has ticks&  labels at few specific
points only.
>
> Right now I use do.breaks&  level.colors with somewhat large number of
steps. The problem is that color change point doesn?t necessary correspond to
the value I?d like to label. Since I have many color steps and I don?t need high
precision I generate labels like this
>
> labels<- ifelse( sapply(at,function(x) any(abs(att-x)<.03)) ,
sprintf("depth= %s ft", at), "")
>
> , where `att` has mine points of interest on color scale bar and `at`
corresponds to color change points used with level.colors . It is a bit
inconvenient as I have to adjust threshold `.03`, number of color steps so that
it labels only adjacent color change point with my labels.
>
> Q: Are there any ready to use functions that would generate some kind of
GRaphical OBject with continuous color scale bar/key with custom at/labels such
that it would work with `legend` argument of xyplot from lattice?
>
Hi Mikhail,
I think that color.legend in the plotrix package will do what you are 
asking, but it is in base graphics, and may not work with lattice.

Jim